The present invention relates to a compressor. More specifically, the present invention pertains to oil separating structures for compressors that are used in vehicle air conditioners to separate atomized lubricant in refrigerant gas.
Refrigerant gas in a compressor is compressed and circulated between the compressor and an external circuit to carry heat. Some compressors include an oil separating structure for collecting atomized oil. The collected oil is used for lubricating parts of the compressor. FIGS. 5(a) and 5(b) show such an oil separating structure. The compressor of FIGS. 5(a) and 5(b) includes a housing 101. The housing 101 accommodates a compressing mechanism (not shown). A discharge passage 102 is formed in the housing 101 to conduct refrigerant from the compressing mechanism to an external refrigerant circuit. A recess 103 is defined in the housing 101 and located in the discharge passage 102. The recess 103 has a circular cross-section and extends in the axial direction of the compressor. A plug 104 includes a first flange 105, second flange 106 and a cylinder 107, which connects the flanges 105, 106. The plug 104 is inserted into the recess 103 from the left, as viewed in FIG. 5(a). Specifically, the plug 104 is press fitted in the recess 103 such that the first flange 105 contacts a positioning step 103b defined on the inner wall 103a of the recess 103.
An annular groove 103c is formed in the wall of the recess 103 at the open end. A snap ring 108 is engaged with the annular groove 103c. Specifically, the peripheral portion 108a of the snap ring 108 is fitted in the groove 103c. The cross section of the snap ring 108 is tapered such that its axial dimension decreases toward the periphery. The plug 104 is held between the snap ring 108 and the step 103b. The snap ring 108 prevents the plug 104 from disengaging from the recess 103.
Dimensional errors may vary the distance d between the groove 103c and the step 103b. However, the plug 104 is still securely held between the snap ring 108 and the step 103b, since the radial penetration of the peripheral portion 108a in the groove 103c can vary. This permits variation in the axial location of the plug 104. In FIG. 5(b), a solid line shows the position of the snap ring 108 when the distance d is shorter than the axial dimension h of the plug 104. A broken line shows the position of the snap ring 108 when the distance d is substantially the same as the axial dimension h of the plug 104.
As shown in FIG. 5(a), a separation chamber 109 is defined at the right side of the plug 104 by the first flange 105. Also, the first and second flanges 105, 106 define the ends of an annular chamber 110. An outlet passage 111 is formed in the first flange 105 and the cylinder 107 to connect the separation chamber 109 with the annular chamber 110. The separation chamber 109 is exposed to the discharge pressure of the compressor. The separation chamber 109 is connected to a low pressure zone by an oil return passage 112 formed in the housing 101. The low pressure zone is an area where the pressure is lower than the discharge pressure.
Refrigerant gas is discharged to the external circuit from the compressor via the discharge passage 102. Before being discharged, the gas flows along the inner wall 103a of the separation chamber 109. Centrifugal force separates atomized lubricant from the gas. The gas is then discharged to the external circuit via the outlet passage 111 and the annular chamber 110. Due to the pressure difference between the separation chamber 109 and the low pressure zone, the separated oil is returned to the low pressure zone via the return passage 112. The oil is then supplied to parts in the compressor to lubricate and cool the parts.
However, due to machining errors, the distance d between the groove 103c and the step 103b can be far shorter than the axial dimension h of the plug 104. In this case, the snap ring 108 cannot be fitted in the groove 103c.
Further, if the distance d is greater than the axial dimension h, the plug 104 will not be firmly held between the snap ring 108 and the step 103b. In this case, the plug 104 can be rotated along with the flow of refrigerant gas in the separation chamber 109, which causes the circumferential surfaces 105a, 106a of the first and second flanges 105, 106 to slide on the inner surface 103a of the recess 103, which wears the plug 104. Also, if loosely held, the plug 104 chatters in the recess 103, which produces vibration and noise.
To solve this problem, the plug 104 is selected from plugs having different axial dimensions. When assembling the plug 104 in the chamber 103, the distance d between the groove 103c and the step 103b is measured, and a plug 104 having a corresponding axial dimension is selected. In this manner, dimensional errors due to machining accuracy are accommodated by the snap ring 108. Therefore, the assembly of the plug 104 into the recess 103 is complicated.